Coastal Vulnerability to Storms in the Catalan Coast

Este trabajo presenta un marco metodológico para la estimación de la vulnerabilidad costera al impacto de tormentas a dos escalas, regional y local. Se hace una evaluación de la vulnerabilidad costera física mediante la cuantificación de dos componentes: erosión e inundación. Posteriormente, ambos elementos son integrados en un Índice de Vulnerabilidad Costera. La metodología desarrollada cubre los siguientes pasos: (i) clasificación de tormentas, (ii) evaluación de la respuesta inducida en la playa -inundación y erosión- (iii) caracterización de las playas en la zona de estudio (iv) definición del índice de vulnerabilidad costera y (v) evaluación de la vulnerabilidad costera. Estos pasos han sido derivados y aplicados a la costa catalana (Mediterráneo Noroccidental español) y pueden ser adaptados a otras costas. Los resultados obtenidos pueden ser fácilmente utilizados por los gestores costeros para identificar zonas costeras sensibles a una clase de tormenta dada y sus procesos inducidos (inundación, erosión o la combinación de ambos) para decidir donde tomar acciones para mitigar estos impactos.This work presents a methodological framework for the estimation of coastal vulnerability to storm impacts at two scales, regional and local. It estimates the physical coastal vulnerability through the quantification of two components: erosion and flooding. Afterwards the two elements are integrated into the so called Coastal Vulnerability Index. The methodological process covers the following steps: (i) storm classification, (ii) evaluation of the induced beach response -flood and erosion-, (iii) coastal zone characterization, (iv) definition of a coastal vulnerability index to storms and (v) assessment of the coastal vulnerability. These steps have been derived and applied to the Catalan coast (NW Spanish Mediterranean) and can be adapted to other coasts. The obtained results can be used by coastal managers in an easy manner to identify sensitive coastal stretches for a given storm class and the induced processes (flooding, erosion or combination of both) with the purpose to take actions and mitigate these impacts

Regional vulnerability analysis of Catalan beaches to storms

A framework to estimate coastal vulnerability to storm impacts at a regional scale is presented. It assesses the physical coastal vulnerability to storm impacts by separately estimating two components: flooding and erosion. It covers the following steps: (i)characterization of the forcing, (ii) evaluation of the induced beach response – inundation and erosion – (hazards quantification), (iii) coastal zone characterization, (iv) definition of a coastal vulnerability index to storms – a composite of two partial vulnerability estimations, the flood vulnerability and the erosion vulnerability indices-, and (v) assessment of the coastal vulnerability. Instead of assessing the vulnerability associated with a given storm, the forcing is defined in terms of representative storms which are obtained by classifying storms in the area using a 5-class system similar to that used for hurricanes (weak, moderate, significant, severe and extreme). Later, a vulnerability assessment for the entire coast to each storm category is produced. The method has been derived for and applied to the Catalan coast (NW Mediterranean) but can be easily adapted to other coasts. It permits managers to identify 3 coastal stretches sensitive to a given storm class for a given induced hazard (flooding, erosion or combination of both) to decide where to take actions.Peer ReviewedPreprin

Regional vulnerability analysis of Catalan beaches to storms

A framework to estimate coastal vulnerability to storm impacts at a regional scale is presented. It assesses the physical coastal vulnerability to storm impacts by separately estimating two components: flooding and erosion. It covers the following steps: (i)characterization of the forcing, (ii) evaluation of the induced beach response – inundation and erosion – (hazards quantification), (iii) coastal zone characterization, (iv) definition of a coastal vulnerability index to storms – a composite of two partial vulnerability estimations, the flood vulnerability and the erosion vulnerability indices-, and (v) assessment of the coastal vulnerability. Instead of assessing the vulnerability associated with a given storm, the forcing is defined in terms of representative storms which are obtained by classifying storms in the area using a 5-class system similar to that used for hurricanes (weak, moderate, significant, severe and extreme). Later, a vulnerability assessment for the entire coast to each storm category is produced. The method has been derived for and applied to the Catalan coast (NW Mediterranean) but can be easily adapted to other coasts. It permits managers to identify 3 coastal stretches sensitive to a given storm class for a given induced hazard (flooding, erosion or combination of both) to decide where to take actions.Peer Reviewe

Morphodynamic Response to Low-Crested Detached Breakwaters on a Sea Breeze-Dominated Coast

Low-crested detached breakwaters (LCDBs) have been widely employed as a mitigation measure against beach erosion. However, only a few studies have assessed their performance in sea-breeze-dominated environments. This work investigates the beach morphodynamics behind LCDBs deployed on a micro-tidal sea-breeze-dominated beach. The study area, located in the northern Yucatán peninsula, is characterized by low-energy, high-angle waves, which drive a persistent (westward) alongshore sediment transport (O(104) m3/year). High-resolution real-time kinematics global positioning system (GPS) beach surveys were conducted over a one-year period (2017–2018) to investigate the performance of LCDBs at three sites. Moreover, unmanned aerial vehicle flights were employed to evaluate far-field shoreline stability. Field observations revealed a distinct behavior in the three study sites, dependent on the breakwaters’ transmission characteristics, geometry, stability, and shoreline orientation. Impermeable LCDBs, made of sand-filled geosystems, induced significant beach accretion (erosion) in up-(down-)drift areas. On the other hand, permeable LCDBs, made of Reef Ball™ modules, induced moderate beach changes and small erosion in down-drift areas owing to higher transmission coefficients. Measurements of LCDBs’ freeboard height show that sand-filled geosystems’ breakwaters presented a significant loss of sand during the study period, which explains the unexpected beach morphodynamic response on the lee side of the structure. Observations suggest that the study area is highly sensitive to the presence of LCDBs with low transmissivity

Rapid Changes in Permeability: Numerical Investigation into Storm-Driven Pebble Beach Morphodynamics with XBeach-G

This study delves into the morphodynamic changes of pebble beaches in response to storm events, employing a combination of observational and numerical approaches. This research focuses on three extreme events, meticulously examining morhological changes in intertidal topography on the beach of Etretat (Normandy, France). A robust dataset of daily beach topography, derived from video monitoring systems, validates a set of numerical simulations of cross-shore dynamics performed by the process-based model XBeach-G. Our study evaluates the model’s efficacy in estimating beach profile evolution under high-energy conditions and explores its sensitivity to the physical properties of pebbles, including permeability. The results underscore the significance of considering spatial and temporal variations in permeability during storms to enhance the numerical model’s accuracy in predicting pebble beach dynamics. Furthermore, this study advocates for the incorporation of grain size mapping techniques to refine numerical model implementations

Changements saisonniers de la résilience des plages le long d'une île-barrière urbanisée

International audienceBeach width, dune height, and vegetation coverage are key parameters to assess beach resistance and resilience to storms. However, coastal development often causes beach ecosystem degradation due to poor coastal management. We propose a Coastal Resilience Index from Remote Sensors (CRIfRS) for urbanized coasts based on aerial photogrammetry. The study area, located along a 7.8 km stretch of coast on a barrier island, is characterized by persistent alongshore sediment transport and the presence of coastal structures and beach-front houses. Contrary to previous studies, we focus on anthropogenic perturbations (coastal urbanization and coastal structures), instead of hydrodynamic conditions (storms), since erosion in this region is mainly associated with alongshore sediment transport gradients induced by coastal structures. Thus, the CRIfRS is based on the relation of three indicators that affect the beach functionality for coastal protection: beach width, coastal structure influence area, and vegetation coverage. The CRIfRS was divided into five categories: Very Low resilience (VL), Low resilience (L), Medium resilience (M), High resilience (H), and Very High resilience (VH). The CRIfRS presented an important spatial and temporal variability due to changing environmental conditions and the deployment of new coastal structures. For the study period, the percentage of the coast within the VL and L resilience classification increased, whereas the percentage of the coast classified as M, H, and VH resilience decreased. During the winter storm season, the resilience increased mainly due to the cross-shore transport whilst during mean wave conditions (i.e., sea-breeze conditions) the long-shore transport becomes more persistent and thus the coastal structures play an important role interrupting the sediment flux. Additionally, the CRIfRS trajectory shows an overall increase of the L resilience and an overall decrease of the H resilience values. This study highlights the important role of anthropogenic perturbations on the assessment of coastal resilience for highly urbanized coasts. The CRIfRS can help to improve the coastal management by assessing the coastal protection capability of beaches considering both natural and anthropogenic factors